Figure 1 outlines the various steps required to release carotenoids from the food matrix, for carotenoid uptake by
intestinal mucosal cells, and subsequent absorption, transportand metabolism. Mechanisms regulating the following processes are not well understood: 1) the release of carotenoids from the food matrix; 2) the solubilization of carotenoids into micelles; 3) the uptake of carotenoids into intestinal mucosalcells; 4) the absorption of intact carotenoids; 5) the cleavage of pro-VA carotenoids within the enterocyte or within other tissues to yield VA; and 6) the tissue distribution, metabolism
and recycling of carotenoids (Boileau, T. et al. 1999, Castenmiller and West 1998).